The pathophysiology of sickle cell disease is poorly understood despite detailed information about the physical chemistry of hemoglobin S solutions. During the last few years we have been studying the intracellular polymerization process by nuclear magnetic resonance spectroscopy and have detected polymer at high oxygen saturation. The present program is a multifaceted approach to study the rheological effects of polymer formation in red cells using electron microscopy, cell aggregation, cell filterability and cell viscosity measurements. We are using electron microscopy to study the amount and physical properties of the polymer of deoxyhemoglobin S that forms in sickle erythrocytes at various oxygen saturation values. The electron microscopic studies are being correlated with results from nuclear magnetic resonance spectroscopy and other methods to examine the physical, physiological and clinical variables that affect intracellular polymerization of deoxyhemoglobin S. These studies will allow us to test various hypothesis about the pathophysiology of sickle cell disease, specifically the relationship of the amount and length of the polymer to changes in cell rheology. These direct studies of polymer will be correlated with the aggregation, filter ability, and viscosity measurements in an attempt to understand how the amount of polymer and the rate of its formation impedes the flow of blood in the microcirculation of sickle cell patients. To facilitate these studies we are working with BEIB to develop an apparatus which will allow us to measure rheological properties at various oxygen saturation values. We will also try to correlate disease severity with these rheological measurements. In addition, we are studying several possible inhibitors of polymerization, especially analagous of diphosphoglycerate, in a continuing attempt to develop a pharmacological treatment of sickle cell disease and related syndromes.